The best way to improve ball handling is to actually practice dribbling. You'll improve your passing and catching of the ball too because you'll improve your reaction time and get a better feel for the ball and how it comes off the ground at different angles, spins, and velocities. Few people go to the gym to practice their dribbling because it seems tedious. But if you can practice simple dribbling exercises, you give yourself time to really understand the nuances in controlling the ball.
Here are a few exercises that I used over the past few years. They increase in order of difficulty and should be completed in that order. These exercises might seem quite boring at first but if you practice them before more advanced drills, you'll have a much more solid control of the ball and consequently improve your crossovers, first step dribble, hesitation dribbles, etc...
Dribble the ball high up to your chin and slowly lower the apex of the ball down to your knees. In game scenarios, you need to be able to control your dribble at different heights.
Practice the above drill but dribble twice as hard. When you're trying to beat your defender to the basket, your dribble will be dramatically faster and more difficult to control. Dribbling hard will emulate this and improve your reaction time.
Practice the above drill but look at the hoop the entire time. It's obviously important to be able to keep your eyes up when dribbling. Once you become adept at this, you should always practice dribbling without looking at the ground and ball.
Practice the above with forward movement, and gradually increase your speed.
Keep these difficulty levels in mind and try implementing them into different styles of dribbling exercises.
- crossovers in front of you left to right to left
- between the legs alternating left and right foot forward
- between the legs keeping the left and right foot parallel
- behind your back left to right and back
It's important to be flexible in going from one type of dribble to another so try mixing them up: 1111222233334444, 12341234, etc...
Lastly, remember to vary the height of the ball, trying to keep the ball in your hands for various times (cupping the ball without carrying). Increase the intensity and speed of your dribble and once you have the dribble somewhat mastered, look up, bring in movement, and do the exercises until you feel completely comfortable.